THE CEREBRUM. 



555 



pictures are therefore separate, a fact which has led to a division of the 

 visual area into a lower and a higher area. 



It was stated in a previous paragraph that electric stimulation of the 

 sensor areas of the monkey brain is attended by certain motor reactions 

 which vary with the area stimulated. Corresponding areas are believed to 

 be present in the human brain and that their stimulation would be followed 

 by similar motor reactions. Their location is shown in Figs. 252 and 253, 

 and named visual, auditory, olfactory, and gustatory motor. 



The stereo. gnostic area or area of stereognostic perception, by which objects 

 are recognized through their form independent of vision and by the sense of 

 tpuch alone, has been located in the super-parietal convolution and the 

 precuneus (Mills). The existence of such an area is rendered probable by 



FIG. 254. SCHEME OF THE MOTOR AREA OF THE HUMAN BRAIN AND ITS SUBDIVISIONS. (After 



Mills.) 



the fact that cases have been recorded in which there was a loss of this 

 power (astereognosis) unaccompanied by either sensor or motor distur- 

 bances. Post-mortem investigations showed that in these cases there was a 

 destruction of the superior parietal convolution. 



Equilibratory, intonation, and orientation areas have been provisionally 

 located in the spheno-temporal lobe. 



The Motor Areas. The general motor area (Fig. 252) is represented as 

 occupying the pre-central convolution, the base of the super-frontal con- 

 volution, both on its lateral and mesial aspects, and the paracentral lobule. 

 The exclusion of the post-central convolution from the motor area is in ac- 

 cordance with the embryologic researches of Flechsig, which indicate that 

 the efferent fibers which compose the pyramidal tract come from the region 

 anterior to the central fissure, and with the experiments of Sherrington and 

 Grunbaum on the brain of the chimpanzee, which demonstrate that the 

 post-central convolution is absolutely inexcitable to electric stimulation. 



